Doctors in Britain are launching a clinical trial of a groundbreaking stem-cell therapy that aims to halt or reverse the damage caused by multiple sclerosis.

Patients admitted to the trial will be injected with stem cells harvested from their own bone marrow in the hope that the cells home in on and repair areas of their nervous system destroyed by the disease.

Bone marrow is a rich source of stem cells that are known to be capable of repairing many different types of body tissue and organs. Under the therapy, the stem cells will be collected, filtered and grown to great numbers in the lab, before being injected back into the blood stream.

The treatment, if safe and effective, could help some of the 100,000 people with multiple sclerosis in the UK. The condition is the most common, disabling neurological condition in young adults. Early symptoms, including blurred vision, poor co-ordination and balance, typically arise between the ages of 20 - 40.

Multiple Sclerosis occurs when the immune system goes awry and attacks a fatty coating called myelin that surrounds nerves in the brain and spinal cord. Damage to the myelin stops signals from the brain being sent quickly and smoothly around the body. There is as yet no cure.

Scientists received £1m from the MS Society and the UK Stem Cell Foundation for three studies that will investigate whether the treatment is safe. One trial, led by Paolo Muraro at Imperial College is the UK part of an international trial that will involve 150 to 200 people with multiple sclerosis in London, Edinburgh and elsewhere in the US, Canada and Italy.

The other trials, at Queen Mary Hospital, London, and the University of Nottingham, will look at the cells' ability to treat optic neuritis, a symptom of MS that can cause blindness, and differences between stem cells taken from patients with progressive MS and those without the condition.

A previous trial into the safety and feasibility of using bone marrow stem cells to treat MS, led by Neil Scolding, a clinical neuroscientist at Bristol University, was deemed a success last year. In June, a US benefactor donated $1.1m (£675,000) to fund a follow-up trial that will assess how much patients improve after receiving the treatment.

Richard Sykes, chair of the UK Stem Cell Foundation, said the trials brought "much-needed hope" to people affected by the disease.

The medical promise of stem-cell therapies has led to a rise in untested treatments for conditions like multiple sclerosis, which have attracted patients to unregulated clinics overseas. Doctors stressed that no stem-cell therapy has yet been proven for MS anywhere in the world.